Project Summary: Understanding the mechanisms of protein and organelle function and dysfunction in disease requires a detailed and dynamic analysis of molecular structures and interactions in live cells. The long-term goal of my laboratory is to develop tools that reveal these functional elements and apply them to discover significant biology and/or design molecules with useful properties. I am drawn to difficult, complex, multi-disciplinary problems where chemistry can catalyze exciting and non-incremental progress. We strive not simply to develop tools, but also to apply them in innovative ways to acquire new and influential knowledge. This rubric leads us naturally into diverse and emerging scientific areas. Fluorescence spectroscopy features prominently in the three research programs described herein. In two, a fluorescent tool we developed (section A) or innovated (section C) has already identified influential new biology; here future work capitalizes on this knowledge with an eye to translation. In the third, tool development is on- going (section B) but progress-to-date provides a clear roadmap for very exciting future applications.